Burner apparatus



March 5, 1963 F. A. LOEBEL ETAL BURNER APPARATUS 3 Sheets-Sheet 1 FiledSept. 6. 1957 INVE'NTORS. Frederzlok 6211 0968;

BY GZenn/fl C KM, W1

March 5, 1963 F. A. LOEBEL ETAL BURNER APPARATUS s Sheets-Shea 2 FiledSept. 6, 1957 INVENTORS. L'ck @[oefiq 2 5,

fieder March 5, 1963 F. A. LOEBEL ETAL BURNER APPARATUS 5 Sheets-Sheet 3Filed Sept. 6, 1957 IUFZSW ufr hmozkuzh 200.!

United States Patent 3,079,981 BURNER APARATUS Frederick A. Loebel andGlenn D. (Iraig, Milwaukee,

Wis, assignors to Cleaver-Brooks Company, a corporation of WisconsinFiled Sept. 6, 1957, Ser. No. 682,517 6 (Ilaims. ((ll. 158-28) Thisinvention relates to burner apparatus, and more particularly toapparatus for burning oil which is atomized and must be intimately mixedwith air in quantities calculated to promote clean and quiet ignitionand efiicient combustion.

It is a general object of the invention to provide a new and improvedburner apparatus of the type described.

One of the principal problems manufacturing commercial and industrialoil burners lies in providing for satisfactory ignition of the fuel. inorder to achieve continuous efficient combustion of fuel oil overextended periods of operation, the fuel must be intimately mixed with aproper amount of air for supporting combustion, usual- *ly about 20% inexcess of stoichiometric quantity. Intimate mixing of the atomized oiland the combustion air is attained by imparting turbulence to thecombustion air, and introducing the atomized oil into the turbulent airstream, after which combustion occurs in a concentrated area, usuallynear the point of fuel injection.

The air turbulence necessary for intimate mixing of the fuel and airmust occur in an orderly, controlled manner so that there is auniformity of air supply to all sections of the combustion chamber. Inorder to achieve uniform distribution of the air, a diffuser means isemployed in the air supply duct to the combustion chamber which isdesigned to impart a swirling motion to the air to provide the properdegree of turbulence for satisfactory mixing of oil and air. In passingthrough the ditfuser, the air is subjected to a drop in static pressurewhich increases the air velocity. The absolute value of the requiredvelocity of air flowing to the combustion chamber depends upon thevolume of air involved. Generally, as the volume decreases, moreturbulence and higher velocities are required. In burner apparatus ofthe type described herein the air velocity at the diffuser exit is inthe range of about 4,000 to 6,000 feet per minute and While the airpressure drop across the diffuser and the resulting increase in velocitypromote efiicient combustion, the high velocity or" the air makes itextremely diificult to ignite the rapidly moving mixture of oil and air.

In some burners, the problems of ignition are minimized by providing fora continuous operation, reducing the firing rate to a low fire or pilotfire when there is no call for heat, and increasing the firing rate tohigh fire operation when there is a call for heat. However, whereeconomy of operation is an important factor, continuous burner operationis undesirable, and it is preferable to utilize an on-off operationwherein the burner is completely shutdown when there is no call for heatand is reignited when there is a call for heat.

In burners of the capacity here under consideration, having a firingrate of from approximately 6 to 15 galions per hour, where burneroperation is confined to onofi operation, there are several commonpractices of igniting the oil and air mixture. One of these methods isto fully open the oil supply valve instantaneously with the starting ofthe blower motor. This arrangement allows the full quantity of oil toflow to the combustion chamber before the motor and the blower have comeup to full speed. Since ignition must be attempted as soon as fuel fiowbegins, the air is insufficient for complete combusdon during the motorspeed-up period (say for example, to 10 seconds), and there resultsheavy smoking during 3,h79,%l Patented Mar. 5, 1953 the burner starting.In addition to the smoke nuisance, ignition in this manner causes rapidsooting and fouling of the heat transfer surfaces, thus requiringfrequent shutdown for cleaning.

Another practice employed in igniting the fuel for onoii operation maybe described as step firing. This practice involves the use of multiplefuel nozzles controlled by valves which must be opened at pre-setintervals during the fan speed-up period. The timing control for suchvalves must be extremely accurate and is quite intricate, because if thevalves open prematurely heavy smoking results due to an excessivequantity of oil being ignited with insufiicient air, and if any valveopens too late there may be sufiicient combustion air flowing toextinguish the previously lighted nozzle or nozzles. In any case, theadjustments in a burner arrangement of this type are critical.

With the above and other considerations in mind, it is a broad object ofthis invention to provide a new and improved burner apparatus of thetype described wherein ignition is easily achieved in a smooth and cleanfashion so as to eliminate smoking, without the necessity of intricatecontrols requiring accurate adjustments which are critical for :properburner operation.

Another object is to provide a new and improved two stage burnerapparatus including a pilot burner nozzle and one or more main burnernozzles wherein oil is supplied to the pilot nozzle immediately onstarting the blower, when the blower supplies sufficient air for com-:bustion at the pilot nozzle, and wherein the pilot burner is shieldedfor stable firing during full air flow sufi'icient for combustion at thepilot and the main burner nozzles, so that fuel flow to the main burnernozzles may be delay until after the blower attains full speed.

A further object is to provide a new and improved shielded pilot nozzlestructure for use in the main stream of air flowing to a combustionchamber, including a shield for protecting the pilot nozzle dischargefrom disruption in an air flow sufiicient to support main burner firing.

It is also an object of the invention to provide a new and improvedelectric circuitry for automatically efiecting burner ignition in aburner apparatus of the character described.

Another object is to provide, in a burner apparatus of the typedescribed, a circuit for obtaining a novel sequence of operationswherein the blower means for supplying air to the combustion chamber,the means for supplying fuel to the pilot or first stage burner, and theignition means for lighting the pilot burner are all set in operationsimultaneously and function to immediately supply fuel to the pilotburner, to immediately supply air in suficient quantities to supportcombustion at the pilot burner, and to immediately light the pilotburner to obtain a smooth clean ignition with a relatively smallquantity of fuel involved, and wherein supply of fuel to the main burneris delayed until such time as the blower means has attained speedsufdcient to supply air in quantities necessary for combustion at bothburners.

Other objects and advantages will become readily apparent from thefollowing detailed description taken in connection with the accompanyingdrawings, in which:

FIG. 1 is a fragmentary perspective View, partly broken away, or" aboiler structure including a burner apparatus embodying the principlesof the present invention;

FIG. 2 is an enlarged longitudinal vertical section taken through theburner tube of the burner apparatus illustrated in FIG. 1, with parts inelevation, and including a diagrammatic showing of the fluid circuitsfor supplying fuel to the burner nozzles;

FIG. 3 is an end elevational view of the structure illustrated in FIG.2, taken at about the line 33 of FIG. 2;

'FIG. 4 is an enlarged longitudinal sectional view through the pilotburner shield;

FIG. 5 is a right end elevational view of the shield illustrated in FIG.4; and

FIG. 6 is an electric circuit diagram for controlling operation of theburner apparatus illustrated in the preceding figures.

While an illustrative embodiment of the invention is shown in thedrawings and will be described in detail herein, the invention issusceptible of embodiment in many different forms, and it should beunderstood that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended tolimit the invention to the embodiments illustrated. The scope of theinvention will be pointed out in the appended claims.

Referring now to the drawings, as illustrated, the invention is embodiedin a horizontal fire tube boiler which includes a horizontally disposedcylindrical boiler shell 10 which may be supported in any suitablemanner. A horizontally disposed fire tube 11 of suitable metal materialis supported in the lower portion of the boiler shell and provides acombustion chamber. Near the front end of the boiler, in the combustionzone, the fire tube 11 is lined for a portion of its length with asuitable dry oven refractory material 12, and forwardly of therefractory 12 is lined with asuitable insulating refractory material 13.Combustion occurs in the tire tube in the vicinity of refractory 12, andboilers of the type illustrated conventionally include suitablestructure forming multiple passes through the boiler from combustiongases which ultimately pass from the boiler shell through an exhauststack 14.

At the front end of the boiler, the shell 10 is closed by an inner frontboiler door 16 in the form of a circular plate which may be secured inany suitable manner to the shell. In addition to the inner door 16, thefront of the boiler shell is closed by an outer dish-shaped door 18 ofgenerally cylindrical configuration and including a radially outwardlyturned flange 19 which abuts the inner door and which-may be supportedin any suitable manner. Doors 16 and 18 together form an air plenumchamber into which air is drawn from atmosphere and from which air isdischarged to the combustion chamber.

A burner tube 29 of cylindrical configuration is fitted in suitableopenings provided in the inner door 16, the refractory 13 and therefractory '12. One end of the burner tube extends into and opens intothe plenum chamber formed between the doors 16 and 18, and the other endof the burner tube extends to and opens into the combustion chamberformed in the refractory 12 and the fire tube 11. The burner tube may besecured in place as illustrated by means of an integral outwardlyextending flange 21 secured to the inner door 16 by any suitable means.The tube functions as a housing for burner apparatus and also functionsas an air duct for conducting combustion air from the air plenum chamberto the combustion chamber.

The upper portion of the outer door 18 is formed with a circular airinlet opening 23 through which air is drawn into the plenum chamber. Adish-shaped fan motor support 24 is suitably secured to the outer doorconcentrically with the air inlet opening 23 and carries a fan motor 25having a drive shaft on which a fan wheel 26 is secured. The motorsupport 24 is formed with a plurality of air inlet openings 27concentrically arranged about the fan motor and controlled byanadjustable damper means 28 for regulating the size of the openings 27.Operation of the motor 25 causes rotation of the fan wheel 26, drawingcombustion air from atmosphere through the motor support openings 27 andthe inner opening 23 into the central portion of the fan wheel, tobedirected radially of the fan wheel between the fan blades 29 into theplenum chamber.

An air diffuser 30 is positioned in the end of the burner tube 20adjacent the combustion chamber and includes a cylindrical side wallportion 31 which is fitted in the burner tube. At the end of thecylinder wall 31, adjacent the combustion chamber, the diffuser isformed with a difiuser plate 32 which extends transversely across theduct or passage provided by the cylindrical wall 31 and the burner tube20. The diffuser plate is formed with a concentric central opening 33and, outwardly of the central opening, is formed with radially extendingopen ings 34, and adjacent the openings 34, with louvers or baffies 35.In flowing from the plenum chamber to the combustion chamber, air passesthrough the diffuser, and the diffuser functions to impart a swirlingmotion to the air to distribute the air uniformly over the combustionzone to insure efficient combustion of fuel in the combustion chamber.In passing through the diffuser, an air pressure drop is encountered,resulting in an increase in air velocity which promotes eflicientcombustion. Air velocity at the diffuser exit in the burner chosenforillustration is in the range of 4,000 to 6,000 feet per minute.

As best seen in FIGS. 2 and 3, the burner apparatus includes a pair ofmain burner nozzles 38 which are centrally located in the burner tube 20and centrally of the central opening 33 in the diffuser plate, with thetips of the nozzles displaced slightly inwardly from the end of theburner tube adjacent the combustion chamber. Positioned centrallybetween the main burner nozzles 38 and thereabove, there is provided apilot burner nozzle 39 which is utilized for igniting fuel dischargedfrom the main burner nozzles. Fuel discharged from the pilot nozzle 39is ignited by suitable ignition means including a pair of ignitionelectrodes 40 disposed slightly below the tip of the pilot nozzle andone slightly to each side of the nozzle. s

The main burner nozzles 38 are supported on the end of a main burnerfuel supply pipe 42, and the pilot burner nozzle is supported on the endof a pilot fuel supply pipe 43. The fuel supply pipes 42 and 43 are inturn supported on a spider structure 44 through which the pipes pass.The spider includes three equally spaced radially extending legs 45which project outwardly from a central hub portion and have their outerends secured to the cylindrical wall 31 of the diffuser. The fuel supplypipes 42 and 43 extend from the nozzles to a mounting plate or closuremember 47, through the member 47, and are suitably secured thereto sothat the plate 47 functions as a support for the pipes. The plate 47 inturn may be removably secured by any suitable means to the outside ofthe outer boiler door 18 and fits over an opening 48 in the outer doorwhich permits removal ofthe burner nozzles on removal of the plate 47.EX- ternally of the plate 47, the fuel lines 42 and 43 connectrespectively with supply conduits 42a and 43a in turn connected with afuel supply system.

Referring to the fluid fuel circuit diagram of FIG. 2, the means forsupplying fuel to the main burner nozzles and the pilot burner nozzleincludes a pump 50 which may desirably be mounted on the outside of theouter boiler door 18, and which is connected to be driven by abelt-drive 51 from the shaft of the fan wheel 26 to the drive shaft ofthe pump. The pump 50 draws fuel oil through on intake line 52 from areservoir 53, and discharges fuel under pressure to a delivery line 54.The pump 50 is of a standard manufacture, and includes a pressureregulating valve incorporated therein which blocks the flow of fuel fromthe pump to the delivery line 54 until a pressure of approximatelypounds per square inch has been attained within the pump, where'- uponthe valve opens to permit flow to the delivery line. The pressurenecessary to open the pressure regulating valve is normally attainedwithin about 1 second after the drive motor 25 starts, and willthereafter function to supply oil to the atomizing nozzles at an oilatomizing pressure, normally about .100 pounds per square inch. Fuelpumped in excess of that required at the burner nozzles is relievedthrough a relief valve incorporated in the pump, and returns to thereservoir 53 through a return line 55.

The pump delivery line 54 connects with a T-fitting 57 which in turn isconnected to the branch line 42a leading to the main burner nozzles andthe branch line 43a leading to the pilot nozzle. A normally closedsolenoid operable valve 58 is provided in the delivery line 54 forcontrolling the flow of fuel to the fitting 57 and to the pilot nozzle39. A normally closed solenoid perable valve 59 is provided in thebranch conduit 42a for controlling the flow of fluid to the main burnernozzles 38.

As previously set forth, the burner apparatus illustrated is arranged tooperate on an on-0E principle only, in order to achieve low costoperation. Ignition of the fuel oil at th full firing rate, inquantities varying from 6 to gallons per hour, is extremely hazardousand noisy, and has never been accomplished in a satisfactory man ner.The provision of a pilot burner makes use of a small quantity of fuelwhich must be initially ignited, and is particularly desirable in burnerapparatus operating on the on-off principle, provided that smooth, quietignition of the small quantity of fuel can be attained, and providedthat smooth, quiet ignition of the remaining fuel at the full firingrate can be obtained from the pilot fire.

Accordingly, in operation, as will be described in more detail indescribing the wiring diagram, the drive motor 2.5 for the blower andthe pump Si) is energized, and within 1 second after the drive motorstarts, oil begins to flow toward the pilot nozzle 39. At the same timethe drive motor 255 is energized, the solenoid operated valve 58 is alsoenergized to open the pump delivery line 54, permitting oil how to thepilot nozzle at a pilot firing rate of about 2 gallons per hour.Simultaneously with energization of the drive motor and the valve 58,the ignition means it? is energized. By the time fuel oil reaches thepilot nozzle 39, the blower has attained sufficient speed to supply theair necessary to support combustion of fuel issuing from the pilotnozzle. Since the ignition means is energized, a fiame is immediatelyestablished at the pilot nozzle in a quiet, and safe manner.

In order to achieve a smooth ignition of the remaining fuel at the mainburner nozzles with a full firing rate, it is desirable to delay theflow of fuel to the main nozzle until such time as the blower hasattained a speed sufficient to deliver air to the combustion chamber inquantities necessary to support combustion at all the nozzles. If fuelflows to the main burner nozzle before the air supplied is suificient tosupport combustion at these nozzles, ignition of the fuel will beaccompanied by excessive smoking. Thus, opening of the solenoid operatedvalve 59 in the burner conduit 42a is delayed for a predetermined timeafter the blower starts, about 4 to 7 seconds, so that ignition of theremaining fuel at the full firing rate will be accomplished in asuitable fashion. One or" the problems encountered in such an operationis that of maintaining the pilot fire, before the main burner nozzlesare lighted, in an air flow great y in excess of that equired forcombustion at the pilot burner, as much as 430% in excess of the airrequired for pilot firing.

According to the invention, a shield 60 is provided for the pilot nozzlein order to maintain stable firing at the pilot nozzle until such timeas the main burners are ignited. As seen best in FIGS. 2 and 3, thepilot nozzle 3? comprises a cylindrical pilot nozzle body 61 having arear end portion adapted to be joined to the supply pipe 33 to receivefuel oil therefrom. At the forward end of the noz:-e body 61, a nozzletip 62 is suitably affixed to th nozzle body as by being threadedtherein for example, and includes a discharge orifice 63 from which fueloil in an atomized state issues in a cone shaped spray substantially asillustrated at 64 (FIG. 2). The pilot burner noule 3? is positioned sothat the orifice 63 is disposed 6 just inside the upper edge of thecentral opening 53 in the diffuser plate 32, as seen best in FIGS. 2 and3.

The pilot nozzle shield 6% comprises an essentially cylindrical partincluding an intermediate portion 65 which is threaded on the outside ofthe nozzle body 61, a rear end portion as which is internally threadedto receive the end of the fuel supply pipe 43, and a forward end portion67 which encircles the nozzle tip 62 in slightly spaced relationthereto. The rear end portion 66 is preferably flattened atdiametrically spaced positions, as illustrated at 650, to receive awrench or tool. The forward open end of the shield abuts against therear face of the diffuser plate 32 and is positioned so that an upperportion, approximately the upper half, of the open end of the shield,above the discharge orifice 63, is closed by the difiuser plate 32.

The construction and arrangement of the shield 69 is such that itshields the nozzle tip and protects the cone shaped spray issuing fromthe nozzle from dissipation by the main air stream at a full flow ratesufficient to support combustion at all the burner nozzles. The coneshaped spray 64 issuing from the pilot nozzle is initially ignited Whilethe air flow is relatively low, at a value not greatly in excess of thatrequired for pilot fire operation. Ignition occurs quietly and cleanly.Once the flame is established, and burning with a base locatedapproximately at the position illustrated at 7t (FIG. 2.) the flame willcontinue to burn further downstream from the base of the flame even in amore turbulent air zone after the air flow increases to a valuesufficient for full firing. The shield protects at least a portion ofthe cone shaped spray from dissipation in the main air stream andprovides a relatively quiescent air zone at the base of the pilot flame.

When fuel flow to the main burner nozzle 38 is established, thesenozzles discharge atomized oil in cone shaped spra s 64a similar to thepilot nozzle discharge. These sprays intersect the burning pilot nozzlefuel and are ignited thereby to burn with bases located approximately asillustrated at 7 9a. Ignition or" the main burners is quiet and smoothwithout excessive smoking. After this, the flame continues to burn fuelsupplied by all the nozzles.

Shielding of the pilot nozzle in the manner described normally wouldcause eddy currents within the pilot nozzle shield causing a deposit ofoil and soot on the nozzle tip surfaces during main burner operation. Inorder to prevent the deposition of soot, oil, and other extraneousmatter on the nozzle tip, the nozzle shield is provided with annularseries of radial openings 71 leading to the interior of the shieldadjacent the nozzle tip. The openings 751 permit a uniform flow of airthrough the shield over the nozzle tip in quantities insufiicient tosupport combustion at the pilot nozzle but in quantities sufficient toprevent sooting. Accordingly, the pilot nozzle burns clean and cool evenduring operation of the main burner nozzles.

Additionally, the shield 69 serves to enclose the pilot nozzle and toprotect the latter from heat radiating toward the nozzle from hotrefractories on burner shutdown, and thus prevents coking of oil in thenozzle passages due to the radiating heat and thereby prevents pluggingof the nozzle passages.

Additionally, the flow of air through the nozzle shield over the nozzletip in quantities insufficient to hamper operation of the nozzle butsufficient to prevent sooting also serves to prevent sooting on theignition electrodes it, so that the electrodes remain clean and free ofsoot for extended periods of operation.

The burner apparatus illustrated and described was tested on acontinuous cycle for a period of about 960 hours, during which timeabout 5000 ignition cycles were completed. No difficulties wereencountered in burner operation, and the pilot nozzle remained free ofsoot and carbon.

The ignition electrodes 4% are conductive sparking elements having majorportions suitably encased in insulators 73 which are held by a mountingbracket 73a in turn supported on the main burner supply pipe 42. Theends of the ignition electrodes remote from the combustion chamher areconnected with suitable conductors 74 in turn connected with conductors'75 encased in insulators 75a passing through the closure plate 47.Externally of the outer door 18, the conductors 75 are connected bywiring 76 (FIG. 1) to an ignition transformer 77 supported on the door18. The ignition transformer is connected in the electric circuit to bedescribed.

A flame detecting photocell 78 is supported by the closure plate 47 inthe burner tube 20' to detect the presence of a pilot flame as acondition precedent to the opening of the main fuel valve 59, thoughthis forms no part of the present invention. The photocell is suitablyconnected in the wiring diagram to perform the desired function, asdescribed below.

Referring now to the wiring diagram of Fig. 6, the electric circuits forobtaining operation of the burner apparatus described include theelectrically operated elements previously referred to, including theblower and pump motor 25, the ignition electrodes 40, the ignitiontransformer 77, the solenoid operated pilot fuel valve 57, the solenoidoperated main fuel valve 59, and the photocell 78. Additionally, thecircuit includes a control unit 84 of conventional manufacture,sometimes described as a program relay, a manually controllable burnerswitch 81, a timer 82, a relay 83 controlled by the timer, and'a starterrelay 84 for the motor 25. Further, the circuit may include, if desired,conventional limit control switches illustrated at 85 and 86, and a roomthermostatic switch 87 for automatically controlling the circuit.Alternatively, the switches 85, 86 and 87 may be omitted if desired andcontrol maintained over the circuit through the manually operated switch81.

The control unit 80 which per se forms no part of the present inventionincludes a network of wiring not entirely illustrated, but a portion ofwhich is illustrated in order to facilitate an understanding of thecircuit .operation, including a transformer 90 for supplying power to aload relay LR controlling normally open switch contacts LR-l which areclosed on energization of the coil LR. Also included in the control unitis a transformer 91 for supplying power to'an electronic networkillustrated generally at 92 which is responsive to the photocell 73 ondetection of a pilot flame to energize a flame relay FR controllingnormally open switch contacts FR-l which are closed when the flame relayis energized.

The timer 82 is a device of conventional construction which includes atimer motor having a winding illustrated at 94 which, when energized,eifects operation of the timer motor and suitable means driven thereby,such as a cam, for closing a normally open switch 95 after apredetermined time delay following energization of the winding 94. Ondeenergization of the motor winding, the operator for the switch 95 isautomatically returned to its starting position by means such as aspring.

The control relay 83 is also a unit of conventional construction, andincludes 4 pairs of stationary switch contacts, the pairs beingidentified respectively by the reference numbers 96, 97, 98 and 99. Amovable switch contact 100 is arranged for cooperation with the contacts96 and 97, and a movable contact 101 is arranged for cooperation withthe contacts 98 and 99. The movable contacts 100 and 1G1 are normallypositioned as illustrated, and are controlled by a relay coil 102, whichon energization is effective to move the movable contacts from thepositions illustrated, in engagement with stationary contacts 96 and 98,to positions engaging the stationary contacts 97 and 99. The relay is ofthe make before break type in which the contacts 97 are closed by themovable contact 101 before the contacts 96 are 3 opened, and thecontacts 99 are closed by the movable contact 191 before the contacts 98are opened.

The starter relay 84 for the blower and the pump motor 25 includes arelay coil 104 controlling a normally open switch 195 which is closed onenergization of the winding 104.

It is believed that the remaining portions of the wiring diagram will bebest understood in describing the operation of the circuit. Accordingly,these will not be described in detail except as follows in thedescription of operation.

In operation, if the room thermostatic switch 87 is employed to controlthe circuit, the manually controllable burner switch 81 will normallyremain closed at all times in order to permit control by the roomthermostatic switch. If the room thermostatic switch is not employed,the circuit will be controlled by manually closing and opening theburner switch 81.

Assuming that the room thermostatic switch and the burner switch areboth closed, a circuit will be completed from a suitable source ofelectric power through a wire 107, a wire 108, a wire 109, the primarywinding of transformer 90, a wire 110, a wire 111, the limit switches 35and 86, the thermostatic switch 87, the burner switch 81a, a wire 112,and a wire 113, back to the source of power to energize the transformer90. En ergization of the transformer is effective to energize the loadrelay winding LR to close the relay switch contacts LR-l.

On closure of the switch LR-l, a circuit is completed to energize thestarter relay for the motor 25, to energize the timer motor winding 94,to energize the ignition transformer 77, and to energize the pilot fuelvalve 57.

The circuit for energizing the starter relay 84 can be tracedfrom thesupply line 107, a wire 115, burner switch 81b, a wire 116, a wire 117,the relay winding 194, a wire 118, a wire 119, the switch contacts LR-l,and wire 111 back to the source of power. Energizetion of the starterrelay coil'104 is effective to complete a circuit from a source of powerthrough a wire 121, the relay switch 105, a wire 122, the motor 25, anda wire 123 back to the source of power,to thereby energize the motor 25for driving the blower and fuel pump.

The circuit for energizing the timer motor winding 94 can be traced fromthe wire 115, burner switch 81b, a wire 125, the timer motor winding 94,a wire 126, relay contacts 98 and 101, a wire 127, a wire 128, and thewire 118 back to the source of power, to thereby energize the timermotor and to begin the predetermined time delay after which the mainfuel valve is opened.

The circuit for energizing the ignition transformer can be traced fromthe burner switch 811), a wire 130, the primary of the ignitiontransformer, a wire 131, and relay contacts 98 and 191 back to thesource of power.

The circuit for energizing the pilot fuel valve may be traced from thewire 130, a wire 132, the valve 57, a wire 133, relay contacts 96 and100, a wire 134, and the wire 127 back to the source of power.

The blower and fuel pump are thereby started in operation, the pilotfuel valve is opened and the ignition transformer is energized toimmediately effect the flow of fuel and air to the pilot burner nozzleand to immediately ignite the combustible mixture of fuel and air toestablish a pilot flame. Oil flows to the pilot nozzle at a pilot orfirst stage firing rate, about 2 gallons per hour in the modelillustrated.

On establishing a pilot flame, the flame is sensed by the photocell 78and the sensing of the flame is reflected in energization of the flamerelay FR which upon energization eifects closure of the switch contactsFR-l to partially complete a circuit to the main fuel valve 59.

During the time that the pilot flame is being established, and theblower is attaining a speed suficient to supply air necessary forcombustion at all the burners, the timer 82 continues to operate for apredetermined time. After the predetermined time passes, the timerswitch 95 is closed to complete a circuit energizing the relay winding102 of the control relay The circuit to the winding 1G2 can be tracedfrom the wire 116, through the winding 102, a wire 136, the time switch95, a wire 137, and the wire 127 back to the source of power.Energization of the winding effects closure of the movable relaycontacts 199 and 161 with stationary contacts 97 and 99 and, later, theopening of contacts 96 and 98.

On energization of the relay winding H32, a holding circuit is completedto maintain the winding energized, and a circuit is completed to themain fuel valve 59.

The holding circuit for maintaining the winding 102 energized can betraced from the wire 116, through the winding 192, a wire 139, the relaycontacts 99 and 101, and the wire 128 back to the source of power.

The circuit for energizing the main fuel valve can be traced from thewire 13%, a wire 141, the valve 59, a wire 142, relay contacts 97 and1%, a wire 143, the switch contacts FR-l and the wire 119, back to thesource of power. The main fuel valve 59 is thereby opened to permit flowof fuel to the main burner nozzles 38 for ignition of this fuel by thepreviously established pilot flame.

After the movable switch 101 of the control relay closes the stationarycontacts 99, the stationary contacts 98 are opened to break the circuitto the timer motor winding Q4 and to break the circuit through theignition transformer 77. The timer motor and the transformer are therebydeenergized. The ignition transformer remains de-energized duringcontinued operation of the burner apparatus for economy of operation.

After the movable switch contact 100 of the control relay closes thestationary contacts 97, the stationary contacts 96 are opened, breakingthe circuit therethrough to the pilot fuel valve 57. Thereafter, thepilot fuel valve is maintained energized by a circuit through the wire133, a wire 145, the wire 143, and the flame relay contacts FR-l. In theevent that a pilot flame has not been established, the pilot fuel valvewill be deenergized on energization of the control relay 93, becausecontacts FR-l will not have been closed.

After a flame is established at the main burner nozzles 38, as describedabove, the nozzles, together with the pilot nozzle 39 continue inoperation until such time as the demand for heat has been satisfied, andeither the thermostatic switch 87 or the manually controled burnerswitch 81 is opened, whereupon burner operation is terminated.

In the event that no flame is established at the pilot burner nozzleupon completion of the pre-determined time delay provided by the timer32, the photocell will not have sensed a pilot flame, the flame relay FRwill not have been energized, the switch contacts FR-l will not havebeen closed, and no circuit can be completed to the main fuel valve 59on energization of the control relay S3 at the end of the predeterminedtime delay. Thus, the fuel supply to the combustion chamber through themain burner nozzles will not be initiated, and a described above, thepilot fuel valve 57 will be deenergized to stop the flow of fuel throughthe pilot nozzle.

In addition to the flame detection upon which main burner operation iscontingent, the control unit 8! may include a safety switch (notillustrated) substantially as described in the Marshall et al. Patent2,748,845, operative on failure of energization of the flame relay PR toalso cause deenergization of the load relay LR, thereby permitting thecontacts LR1 to open and deenergize the entire electric circuit andterminate the burner operation.

We claim:

1. An oil burner apparatus, comprising, a burner tube for conducting airto a combustion chamber, an air diffuser plate across the burner tube atthe forward end portion thereof having a central opening therethroughand additional openings disposed radially outward from the centralopening and means adjacent the outwardly disposed openings for directingair forwardly therethrough in a swirling pattern, a main oil nozzlelocated in the burner tube adjacent the diffuser plate and centrally ofsaid central opening to direct atomized oil forwardly therethrough, apilot oil nozzle located in the burner tube slightly to the rear of saiddiffuser plate and adjacent the edge of said central opening to directatomized oil therethrough, and a cylindrical pilot nozzle shieldsurrounding the pilot nozzle, having a rear end on the nozzle body,having an open forward end around the nozzle tip, and having an upperportion of its forward edge adjacent the rear face of said diifuserplate, thereby to shield the pilot nozzle for pilot firing in the mainair stream during full air flow suflicient to support main burner firingbefore firing of the main burner.

2. An oil burner apparatus, comprising, a burner tube for conducting airto a combustion chamber, an air diffuser plate across the burner tube atthe forwrad end portion thereof having a central opening therethroughand a series of openings disposed radially outward from the centralopening and bafiles adjacent the outwardly disposed openings fordirecting air forwardly therethrough in a swirling pattern, a main oilnozzle located in the burner tube slightly to the rear of the difiuserplate and centrally of said central opening to direct atomized oilforwardly therethrough, a pilot nozzle located in the burner tubeslightly to the rear of said diffuser plate and adjacent the edge ofsaid central opening to direct atomized oil therethrough, and acylindrical pilot nozzle shield surrounding the pilot nozzle, closed atthe rear end, having an open forward end encircling the nozzle tip, andhaving a portion of its forward edge abutting said diffuser plate sothat a portion of the open forward end thereof is closed by the difiuserplate, the construction and arrangement of the shield serving to shieldthe pilot nozzle for stable pilot firing during full air flowsufiicien-t to support cornbustion at both burners, said shield having aplurality of openings adjacent the nozzle tip to permit a uniform flowof air through the shield over the pilot nozzle tip to prevent depositof oil and soot on the nozzle tip during operation of the main burner.

3. An oil burner apparatus, comprising a burner tube for conductin. airto a combustion chamber, an air diffuser plate extending across theburner tube at the forward end portion thereof having a central openingtherethrough and a series of radially extending openings therein andbaffles adjacent the radial openings for directing air forwardlytherethrough in a swirling pattern, a main oil nozzle located in theburner tube slightly to the rear of the diffuser plate and centrally ofsaid center opening to direct atomized oil forwardly therethrough, apilot oil nozzlc located in the burner tube slightly to the rear of saiddifi'user plate and above the main oil nozzle to direct atomized oilthrough said central opening, said pilot nozzle compr sing a cylindricalnozzle body adapted to be connected at the rear end to an oil supplypipe and an oil atomizing nozzle tip afliaed to the forward end of thenozzle body, and a cylindrical pilot nozzle shield surrounding the pilotnozzle, having a rear end fitted on the nozzle body, having an openforward end encircling the pilot nozzle tip in slightly spaced relationthereto, and having an upper portion of its forward edge abutting therear face of the difiuser plate to shield the pilot nozzle for pilotfiring during full air flow suflicient to support combastion at bothburners, said shield having a series of radial openings adjacent thenozzle tip to permit air to flow over the nozzle tip in quantitessuflicient to prevent deposit of oil on the nozzle tip during operationof both burners.

4. An oil burner, comprising, a cylindrical housing forming a combustionchamber, a cylindrical burner tube having an open rear end and a forwardend positioned adjacent the combustion chamber to provide an air ductfor conducting air to ilow in a stream from the rear end to thecombustion chamber for mixture with atomized oil to support combustionof the oil, an air diffuser plate across the burner tube at the forwardend portion thereof in the air stream having a central openingtherethrough and series of radially extending openings therein andbaffies adjacent the radial openings for directing air forwardlytherethrough in a swirling pattern, a pair of main oil atomizing nozzleslocated side by side in the burner tube slightly to the rear of thediffuser plate and substantially centrally'of said central opening todirect atomized oil therethrough, a pilot oil atomizing nozzle locatedabove and intermediate said main nozzles slightly to the rear of thediffuser plate and positioned to direct atomized oil through saidcentral opening adjacent the upper edge thereof, and a cylindrical pilotnozzle shield surrounding the pilot nozzle, closed at the rear end,having an open forward end encircling the pilot-nozzle tip, and havingan upper portion'of'it's forward edge abutting the rear face of thediifuser plate to shield the pilot nozzle for pilot firing in the main'air stream during full air flow sufficient to support combustion at thepilot and main burners.

5. An oil burner, comprising, a cylindrical housing forming a combustionchamber, a coaxial cylindrical burner tube having an open rear end and aforward end positioned adjacent one end of the combustion chamber toprovide an air duct for conducting air to flow in a stream from the rearend to the combustion chamber for mixture with atomized oil to supportcombustion of the oil, an air diifuser plate across the forward end ofthe burner tube inthe air stream having a central opening therethroughand an annular series of radially extending openings therein andbafiiles adjacent the radial openings for directing air forwardlytherethrough in a swirling pattern, a pair of main oil atomizing nozzleslocated side by side in the burner tube slightly to the rear of thediffuser plate and substantially centrally of said central opening todirect atomized oil therethrough, a pilot oil atomizing nozzle locatedabove and intermediate said main nozzles slightly to the rear of thediffuser plate and positioned to direct atomized oil through saidcentral opening adjacent the upper edge thereof, said pilot nozzlecomprising a cylindrical nozzle body adapted to be connected at the rearend to an oil supply pipe and an oil atomizing nozzle tip aflixed to theforward end of the nozzle body, a pair of ignition electrodes positionedslightly forwardly of slightly below the pilot nozzle tip, one slightlyto each side of the nozzle tip, and a cylindrical pilot nozzle shieldsurrounding the pilot nozzle and extending the length of the nozzle,having a rear end fitted on the nozzle body and an open forward endencircling the nozzle tip in slightly spaced relation thereto, saidshield having approximately the upper half of its forward end abuttingthe rear fiace of the diffuser plate, the construction and arrangementof the shield serving to shield the pilot nozzle for stablepilot firingin the main air stream during full air flow sufficient to support mainburner operation befiore and during firing of the main burners, saidshield having an annular series of radial openings adjacent the nozzletip to permit an even flow of air through the shield over the pilotnozzle tip in quantit-ies sufiicient to prevent deposit of oil and sooton the nozzle tip during operation of the main burners.

6. A shielded oil atomizing pilot nozzle structure for use with a mainburner nozzle in the main stream of air flowing to a combustionchamberto permit stablepilot firing during full air flow sufiicient tosupport firing at both nozzles, comprising: a pilot nozzle fordischarging atomized oil into a combustion chamber including acylindrical nozzle body having a rear end adapted fior connection withan oil supply conduit, and a nozzle tip aflixed to the forward end ofthe nozzle body for discharging atomized oil in a cone shaped spray; anda cylindrical pilot nozzle shield surrounding the pilot nozzle andextending the length of the nozzle, having a rear end fitted on thenozzle body and an open forward end encircling the nozzle tip inslightly spaced relation thereto, to shield at least at portion of thecone shaped nozzle discharge from the main air stream, said shieldhaving a series of radial openings therethrough adjacent the nozzle tiprearwardly of the discharge onifice therein and forwardly of the rearend fitted on the nozzle body to permit an even flow of air forwardlythrough the shield over the pilot nozz e tip in quantities suflicient toprevent deposit of oil and soot 'on the nozzle tip.

References Cited in the file of this patent UNITED STATES PATENTS1,695,152 Mantindale Dec. 11, 1928 1,843,821 Joslyn Feb. 2, 19322,003,624 Bower June 4, 1935 2,315,412 Galumbeck Mar. 30, 1943 2,655,207Outterson Oct. 13, 1953 2,655,208 Outterson Oct. 13, 1953 2,765,842 LakeOct. 9, 1956 2,806,518 Poole et a1 Sept. 17, 1957 2,865,441 Coupe Dec.23, 1958 2,876,763 Hunter et al. 'Mar. 10, 1959

1. AN OIL BURNER APPARATUS, COMPRISING, A BURNER TUBE FOR CONDUCTING AIRTO A COMBUSTION CHAMBER, AN AIR DIFFUSER PLATE ACROSS THE BURNER TUBE ATTHE FORWARD END PORTION THEREOF HAVING A CENTRAL OPENING THERETHROUGHAND ADDITIONAL OPENINGS DISPOSED RADIALLY OUTWARD FROM THE CENTRALOPENING AND MEANS ADJACENT THE OUTWARDLY DISPOSED OPENINGS FOR DIRECTINGAIR FORWARDLY THERETHROUGH IN A SWIRLING PATTERN, A MAIN OIL NOZZLELOCATED IN THE BURNER TUBE ADJACENT THE DIFFUSER PLATE AND CENTRALLY OFSAID CENTRAL OPENING TO DIRECT ATOMIZED OIL FORWARDLY THERETHROUGH, APILOT OIL NOZZLE LOCATED IN THE BURNER TUBE SLIGHTLY TO THE REAR OF SAIDDIFFUSER PLATE AND ADJACENT THE EDGE OF SAID CENTRAL OPENING TO DIRECTATOMIZED OIL THERETHROUGH, AND A CYLINDRICAL PILOT NOZZLE SHIELDSURROUNDING THE PILOT NOZZLE, HAVING A REAR END ON THE NOZZLE BODY,HAVING AN OPEN FORWARD END AROUND THE NOZZLE TIP, AND HAVING AN UPPERPORTION OF ITS FORWARD EDGE ADJACENT THE REAR FACE OF SAID DIFFUSERPLATE, THEREBY TO SHIELD THE PILOT NOZZLE FOR PILOT FIRING IN THE MAINAIR STREAM DURING FULL AIR FLOW SUFFICIENT TO SUPPORT MAIN BURNER FIRINGBEFORE FIRING OF THE MAIN BURNER.